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    Characterization of hollow chemical garden fibers from metal salts and water glass
    (Kluwer Academic Publ, 2002) Balkose, D; Ozkan, F; Kokturk, U; Ulutan, S; Ulku, S; Nisli, G
    Hollow fibers formed from water glass and metal salts of IIA(Ca), VIIB(Fe, Co, Ni) and IB(Cu) groups were characterised in this study. Fragile fibres obtained herein broke down into small pieces during isolation and drying. Quantitative information about morphology, chemical composition and surface structure of the fibres were obtained. The diameter and wall thickness of the fibers were around 50 mu and 3 mu. respectively. They had particulate inner and smooth outer surfaces. Fibers had variable composition with metal (II) oxide/SiO2 ratio in the range 0.31 to 1.02. While group VIIB metal (II) fibres were amorphous, group IIA and IB metal (II) fibres were partially crystalline All the fibres had pores both in micro pore and meso pore region. The B.E.T surface area from N-2 adsorption data was in the range of 10-249 m(3) g(-1) and 8-176 m(2) g(-1) from Langmuir and B.E.T models respectively.
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    Effects of mixed metal stearates on thermal stability of rigid PVC
    (Pergamon-Elsevier Science Ltd, 1999) Gokcel, HI; Balkose, D; Kokturk, U
    As a representative commercial heat stabilizer, Al 4180 was characterized by spectroscopic and thermal analysis techniques and used in thermal stabilization of rigid PVC. Al 4180 was a mixture of stearates of Al(III), Zn(II), Pb(II) and Ca(II) and metal hydroxides such as Al(OH)(3). Observed acceleration of dehydrochlorination of PVC was explained by the inefficient mixing of the stabilizer with PVC and formation of dehydrochlorination catalyst, ZnCl2 and AlCl3 on heating the films. (C) 1999 Elsevier Science Ltd. All rights reserved.
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    Flexible poly(vinyl chloride)-zeolite composites for dye adsorption from aqueous solutions
    (Marcel Dekker Inc, 1996) Balkose, D; Ulutan, S; Ozkan, F; Ulku, S; Kokturk, U
    Flexible poly(vinyl chloride) (PVC) composites having natural zeolite clinoptillolite were prepared by plastisol-plastigel technology. Adsoption of methylene blue on each raw material and on composites was studied both from an equilibrium and a rate approach. It was observed that the adsorption capacity of zeolite decreased when it was embedded in composites. The equilibrium uptake of methylene blue increased with an increasing zeolite fraction in composites. Methylene blue was adsorbed from a 0.02 g . cm(-3) aqueous solution slowly, but was nearly adsorbed completely with a composite having a 0.3 volume fraction of zeolite, The effective diffusion coefficient of methylene blue in composites was of the order of 10(-13) m(2) . s(-1) and decreased with increasing filler fraction.
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    The nature and origin of intraocular metallic foreign bodies appearing after phacoemulsification
    (Karger, 2003) Kose, S; Mentes, J; Uretmen, O; Topcuoglu, N; Kokturk, U; Yilmaz, H
    In order to evaluate the nature and origin of metallic foreign bodies embedded in the iris after uneventful phacoemulsification, we aimed to produce metallic fragments by applying ultrasound power with the same phaco machine and handpiece in an experimental model in vitro. In a glass bottle, we used linear phaco power of 100% continuously for 5 min first with a new phaco tip and then with a used tip. Afterwards, the fluid in the bottle was filtered through a Millipore filter. The remains on the filter were studied by scanning electron microscopy (SEM) and microprobe. Small particles remained on the filter which was used for the new tip. Microprobe micro-analysis showed that these particles were mainly titanium, the same as the phaco tip. SEM of both the new and the used tips showed small fragments on the exterior surface and lumen. Intraocular metallic foreign bodies after phacoemulsification are likely to be shaken loose from the phaco tip. Although it is mostly agreed that these fragments are well tolerated, their overall effect remains to be evaluated in the long term. Copyright (C) 2003 S. Karger AG, Basel.
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    The nature and origin of intraocular metallic foreign bodies appearing after phacoemulsification
    (Karger, 2003) Kose, S; Mentes, J; Uretmen, O; Topcuoglu, N; Kokturk, U; Yilmaz, H
    In order to evaluate the nature and origin of metallic foreign bodies embedded in the iris after uneventful phacoemulsification, we aimed to produce metallic fragments by applying ultrasound power with the same phaco machine and handpiece in an experimental model in vitro. In a glass bottle, we used linear phaco power of 100% continuously for 5 min first with a new phaco tip and then with a used tip. Afterwards, the fluid in the bottle was filtered through a Millipore filter. The remains on the filter were studied by scanning electron microscopy (SEM) and microprobe. Small particles remained on the filter which was used for the new tip. Microprobe micro-analysis showed that these particles were mainly titanium, the same as the phaco tip. SEM of both the new and the used tips showed small fragments on the exterior surface and lumen. Intraocular metallic foreign bodies after phacoemulsification are likely to be shaken loose from the phaco tip. Although it is mostly agreed that these fragments are well tolerated, their overall effect remains to be evaluated in the long term. Copyright (C) 2003 S. Karger AG, Basel.
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    Structure of starch-bentonite gels
    (Dr Dietrich Steinkopff Verlag, 1997) Besun, N; Peker, S; Kokturk, U; Yilmaz, H
    Mixed gels of starch and bentonite are investigated in the interval 0.056-0.089 of total solids/water ratio and 0-100% starch in the solids. The bentonite was a sodium calcium bentonite with a Na/Ca ratio of 1.76. In water it forms gels consisting of a network of band-type structures. Starch forms gels through hydrogen bonds between granules and/or amylose and amylopectin present on the external surfaces of granules and/or in fully stretched form. Mixed gels of bentonite and starch were obtained by adding corn starch granules to the already formed bentonite gels and heating the mixture above the Kofler gelatinization temperature. Amylose and amylopectin were adsorbed on strands of band-type structures of montmorillonite lamellae. Starch gellation, e.g. diffusion of amylose out of the granule, was facilitated in the presence of bentonite, On the other hand. the presence of starch favored delamination of the montmorillonite particle into thinner lamellae, Maximum gelatinization and polymer adsorption were observed for gels with 20% starch and 80% bentonite. Montmorillonite networks formed the continuous phase for 0-80% starch, At higher starch concentrations. montmorillonite flakes were dispersed within the polymer network. increase in the water content of the gels caused segregation of the bentonite and starch.
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    A study of cobaltous chloride dispersion on the surface of the silica gel
    (Elsevier Science Bv, 1999) Balkose, D; Kokturk, U; Yilmaz, H
    Cobalt (II) salts dispersed on different substrates have functions as humidity indicating desiccants and catalysts. CoCl2, containing silica gel granules of 3 mm size for packed column applications were prepared by impregnation of the aqueous solution of the salt to silica hydro gel at pH near 2, drying and ageing methods. X-ray diffraction and electron microprobe studies indicated cobalt element was both dispersed in particulate form and as sub-monolayer. IR spectra indicated presence of Si-OH groups in all of the silica gels. CoCl2, containing silica gels changed colour from blue to pink upon moisture adsorption due to presence of the CoCl2, Co2SiO4 and Na2CoSiO4. (C) 1999 Elsevier Science B.V. All rights reserved.